A flexible interface between DNA ligase and PCNA supports conformational switching and efficient ligation of DNA
A flexible interface between DNA ligase and PCNA supports conformational switching and efficient ligation of DNA
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DOI：
10.1016/j.molcel.2006.08.015
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发表时间：
2006-10-20
期刊：
影响因子：
16
通讯作者：
Ellenberger, Tom
中科院分区：
文献类型：
--
作者：
Pascal, John M.;Tsodikov, Oleg V.;Ellenberger, Tom
DNA滑动夹环绕着DNA，为许多DNA加工酶提供结合位点。然而，很大程度上是未知的滑动钳，如增殖细胞核抗原（PCNA）协调多步DNA交易。我们分别用X射线衍射和小角X射线散射（SAXS）确定了硫磺硫化叶菌DNA连接酶和异源三聚体PCNA的结构。三个不同的PCNA亚基组装成一个类似于人类同源三聚体PCNA的蛋白质环，但具有三个独特的蛋白质结合位点。在没有切口DNA的情况下，硫磺硫化叶菌DNA连接酶具有开放的延伸构象。当与异源三聚体PCNA复合时，DNA连接酶与PCNA 3亚基结合，并且连接酶保持开放的延伸构象。连接酶的封闭环状构象催化DNA末端连接反应，该反应受到PCNA的强烈刺激。DNA连接酶构象中的这种开放到闭合的开关通过与PCNA的可延展界面来调节，所述界面作为DNA连接的有效平台。
DNA sliding clamps encircle DNA and provide binding sites for many DNA-processing enzymes. However, it is largely unknown how sliding clamps like proliferating cell nuclear antigen (PCNA) coordinate multistep DNA transactions. We have determined structures of Sulfolobus solfataricus DNA ligase and heterotrimeric PCNA separately by X-ray diffraction and in complex by small-angle X-ray scattering (SAXS). Three distinct PCNA subunits assemble into a protein ring resembling the homotrimeric PCNA of humans but with three unique protein-binding sites. In the absence of nicked DNA, the Sulfolobus solfataricus DNA ligase has an open, extended conformation. When complexed with heterotrimeric PCNA, the DNA ligase binds to the PCNA3 subunit and ligase retains an open, extended conformation. A closed, ring-shaped conformation of ligase catalyzes a DNA end-joining reaction that is strongly stimulated by PCNA. This open-to-closed switch in the conformation of DNA ligase is accommodated by a malleable interface with PCNA that serves as an efficient platform for DNA ligation.